Motor Drive Device Overvoltage Protection Control
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Solution Overview
Problem
Existing motor drive devices in hybrid and electric vehicles face issues with overvoltage due to failures in the motor or battery, leading to potential damage to circuit elements and loads, and current systems require complex overvoltage determination and delayed switching to phase short-circuit states, which can result in continued degradation and increased costs.
Innovation Solution
A motor drive device with a control system that proactively switches between three-phase short circuit and all-phase shut off based on motor rotation speed and induced voltage to prevent overvoltage, using a failure determination unit and DC power supply state determination unit to manage inverter control and prevent current flow from the motor to the DC power supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electric power conversion device is controlled to establish the phase short-circuit state after overvoltage is determined, then overvoltage can be suppressed and circuit elements can be protected, but time elapses in the overvoltage state causing continued degradation and damage
Solution Approach 1:
The control device proactively transitions to the phase short-circuit state based on predicted conditions (motor rotation speed and induced voltage) before overvoltage actually occurs. This preliminary action prevents the time delay problem by anticipating overvoltage conditions and taking preventive measures in advance, thereby protecting circuit elements without allowing overvoltage to persist.
Solution Approach 2:
The control device applies counter-action in advance by detecting conditions that would lead to overvoltage (such as motor rotation speed exceeding a threshold or induced voltage approaching dangerous levels) and preemptively switching to phase short-circuit mode. This preliminary anti-action neutralizes the harmful overvoltage effect before it can cause degradation or damage to circuit elements.
2Reliability
If overvoltage determination processing is implemented to detect overvoltage conditions, then circuit elements can be protected, but the processing becomes complicated and costs increase
Solution Approach 1:
Instead of implementing complex real-time overvoltage detection and determination processing, the control device uses preliminary thresholds based on motor rotation speed and induced voltage to predict when overvoltage will occur. This approach simplifies the processing by relying on pre-established criteria rather than complex real-time analysis, reducing computational complexity and cost while maintaining protection effectiveness.
Solution Approach 2:
The control device uses simple, easily obtainable parameters (motor rotation speed and induced voltage) as proxies for overvoltage detection, rather than implementing expensive and complex overvoltage determination circuits or sensors. This substitution with cheaper measurement methods reduces system complexity and cost while achieving the same protective function.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively protects the DC power supply and inverter by switching controls before overvoltage occurs, reducing the risk of damage and simplifying processing, thus preventing complications and cost increases associated with delayed switching and complex overvoltage determination.
Implementation Method 1
an inverter configured to convert DC electric power supplied from the DC power supply device into AC electric power, and to convert AC electric power obtained from the motor to DC electric power
Implementation Method 2
current is inhibited from flowing to the power supply side in some cases because, for example, a power supply has a failure or a battery is fully charged
Data Source
AI summary
MCU (2001) determines whether at least one of double three-phase inverter (2030) or battery (2002) has a failure, or battery (2002) is fully charged, and switches control to be performed in inverter (2030) between all-phase shut off and three-phase short circuit based on a motor rotation speed of double three-phase motor (2050) when MCU (2001) determines that any one of inverter (2030) and battery (2002) has a failure, or battery (2002) is fully charged. Battery (2002) and inverter (2030) can be protected when current is inhibited from flowing from motor (2050) to battery (2002) due to a failure of inverter (2030) or battery (2002).